Question
Topic – 8.6 Biodiversity
(a) – Topic – 8.6 Biodiversity
(b) – Topic – 8.1 Responses to the Environment
(c) – Topic – 7.5 Hardy-Weinberg Equilibrium
(d) – Topic – 7.4 Population Genetics
Sand lances of the genus Ammodytes are small fish that function as keystone organisms in several coastal ecosystems. These sand lances are prey fish that support organisms at higher trophic levels. Scientists performed experiments to examine how sand lance populations are likely to be affected by the rising temperatures and \(CO_{2}\) levels associated with climate change.
Sand lance embryos typically develop and mature into adult fish at low temperatures (approximately 5°C) and stable, low CO2 levels (approximately 400 μatm). Over the course of two years, the scientists measured the survival rate of sand lance embryos allowed to develop and mature in a laboratory at three different temperatures, 5°C, 7°C, and 10°C, with the level of \(CO_{2}\) maintained at 400 μatm, 1,000 μatm, and 2,100 μatm for each temperature.
(a) Describe the effect of increased biodiversity on the resilience of an ecosystem in a changing environment.
(b) Justify the scientists’ selecting 5°C as the lowest temperature and 400 μatm as the lowest CO2 level in their study of sand lance embryo survival.
(c) State a null hypothesis for the experiment.
(d) The scientists claim that a reduction in the population size of the Ammodytes sand lances will affect the stability of the entire coastal ecosystem. Provide reasoning to support the scientists’ claim.
▶️Answer/Explanation
3(a) Describe the effect of increased biodiversity on the resilience of an ecosystem in a changing environment.
• (Ecosystem) resilience/it will be greater (with increased biodiversity).
3(b) Justify the scientists’ selecting 5°C as the lowest temperature and 400 μatm as the lowest CO2 level in their study of sand lance embryo survival.
Accept one of the following:
• These are the normal/current conditions at which the embryos develop and were used as a basis for comparison.
• These (current) conditions were used as a basis to compare the effects of changes in environmental conditions/increases in temperature and \(CO_{2}\).
3(c) State a null hypothesis for the experiment.
Accept one of the following:
• Climate change will have no effect on sand lance (embryo) survival/sand lance development/the size of sand lance populations.
• (Increases in) temperature/\(CO_{2}\) levels will have no effect on sand lance (embryo) survival/sand lance development /the size of sand lance populations.
• There will be no difference in the sand lance (embryo) survival rates/sand lance development/the size of sand lance populations measured at all/different temperatures and \(CO_{2}\) levels.
3(d) The scientists claim that a reduction in the population size of the Ammodytes sand lances will affect the stability of the entire coastal ecosystem. Provide reasoning to support the scientists’ claim.
Accept one of the following:
• There will be a negative effect on other trophic levels because the sand lance provides food for many other species.
• There will be a negative effect on other trophic levels because there will be reduced energy to transfer (to higher trophic levels).